Polypropylene projectile-shorting target with wire screen electrodes



y 8, 1969 v J. L. LA MURA' 3,454,277

' POLYPROPYLENE PROJEECTILE-SHORTING TARGET WITH WIRE SCREEN ELECTRODESFiled Sept 12 1967 FIG.\

V G %%%%%%n%y JOSEPH L. LuMURA INVENTOR ATTORNEY United States Patent3,454,277 POLYPROPYLENE PROJECTILE-SHORTING TAR- GET WITH WIRE SCREENELECTRODES Joseph L. La Mura, West Caldwell, N.J., assignor to JoanellLaboratories, Inc., Livingston, N.J., a corporation of New JerseyContinuation-impart of application Ser. No. 588,350, Oct. 21, 1966. Thisapplication Sept. 12, 1967, Ser. No. 667,298 The portion of the term ofthe patent subsequent to Sept. 17, 1985, has been disclaimed Int. Cl.A63b 9/02 US. Cl. 273102.2 2 Claims ABSTRACT OF THE DISCLOSURE A targetfor electrically reporting hits on a target is described. The targetcomprises three panels of propylene polymer foam and two metal wovenscreens, the five layers being securely bonded to each other by theapplication of heat in a hot rolling mill. The recording circuitincludes a detecting means and a pulse delay circuit for transformingthe sharp pulse created by conduction between the two screens into abroad pulse which can be applied to a recorder.

This application is a continuation-in-part of my copending applicationSer. No. 588,350, filed Oct. 21, 1966, now Patent No. 3,401,939.

This invention relates to a target for electrically recording theperforations caused by projectiles such as rifle bullets, projectilesfrom various automatic weapons, and bullets from sub-machine guns. Ithas specific relationship to a target which is impervious to moistureand which will withstand repeated perforations by projectiles.

Many targets have been designed and built for training and testingpurposes. A large percentage of these targets have been constructed offlimsy materials such as corrugated cardboard, styrene foam, and foamrubber. These targets work well for a few projectiles but they do notlast long and a projectile which may strike the target at about the sameposition as a previous projectile, will not produce a recording pulse.In addition, many of the prior art targets are not water proof andtarget practice cannot be held in the rain or in very humid weather.Also prior art targets did not record hits made by an insulated bulletor a bullet covered by paint.

The present target is designed for use in any weather, including drivingrain. The target is made of carefully selected materials which have azero degree of 'Water absorption and any hole made by a projectile willbe closed by the resilient material forming the target laminations and asecond projectile through the same spot will be recorded. The presenttarget is made of an array of layers of plastic foam which contain twometal woven screen electrodes. The foam layers are cast in such a mannerthat a continuous impervious layer is on the outside of each targetsurface so that no moisture can penetrate within the target space.

When an insulated projectile hits the target and passes through themetal screens, the metal wire in the screens is broken apart and thewire ends scrape the paint or insulating cover from the projectile toestablishan electrical contact.

For a better understanding of the present invention, together with otherand further details thereof, reference is made to the followingdescription taken in connection with the accompanying drawings:

FIG. 1 is a front view of the target.

FIG. 2 is a cross sectional view of a portion of the target showing thelaminated construction.

3,454,277 Patented July 8, 1969 FIG. 3 is a cross sectional view similarto FIG. 2 but showing a projectile piercing the target.

FIG. 4 is one form of circuit which may be used in conjunction with thetarget.

Referring now to FIG. 1, the target comprises a laminated array 10 offive layers. The details of the construction are shown in FIG. 2 where afront panel 11 is bonded to a woven metal screen 12. A central panel 13is bonded to the other side of screen 12 and also bonded to a secondwoven metal screen 14. The third layer 15 is bonded to the other side ofscreen 14. It should be noted that the upper end of the target, and alsothe side edges, have the insulating plastic layers bonded togetheraround the ends of the metal screen so that moisture can be kept awayfrom the conductive elements. The bottom portion of the target 16 isformed in a similar manner but at this edge two conductors 17 and 18 arebrought out through the bottom surface for connection to an externalcircuit.

FIG. 3 shows a cross sectional portion of the target similar to FIG. 2but having a projectile 20 moving through the target. It should be notedthat all five layers of the target are displaced by the projectile inthe direction of the projectile motion. The three flexible layers 11,13, and 15 are also compressed by the penetration of the projectile and,after the projectile has left the target, the three foam layers moveback into place and partially seal the hole. The metal screens 12 and 14are torn by the projectile, the ends of the wires scratch the paint fromthe projectile, and form a connection between the electrodes so thatcurrent can pass between them and be recorded by means of anexternalcircuit. There are times 'when wires from the first electrodemay be drawn into contact with the wires in the second electrode to forma shorted connection. The external circuit is arranged so that a largecurrent will then be applied to this short circuit and quickly burn itout to normalize the recorder circuit and condition the target foranother projectile action.

The three foam layers 11, 13, and 15 are made of propylene polymer foamwhich is constructed so that the foam bubbles are very small. One suchmaterial which is suitable for this type of target is commerciallyavailable and may be obtained from Hazeg, Inc., of Wilmington, Del., ascompound Minicel PPF.

A five layer sandwich is formed by the two screens and the three layersof foam as shown in FIG. 2. This array is then passed through heatedrolls and a unitary target is formed by the application of heat alone.The .surfaces of the foam are sealed to the wire mesh and to each otherto form a watertight target.

When the above described target is employed for recording hits byprojectiles, a coupling circuit is connected between the target and arecorder 21. A preferred circuit is shown in FIG. 4 where the targetconductors 17 and 18 are connected to a positive conductor 22 and anindicating lamp 23. A storage battery 19 of about twenty-four volts isconnected across conductors 17 and 18. The other side of the indicatinglamp 23 is connected to a grounded conductor 24 which is also connectedto the negative terminal of a direct current power supply 25. A manuallyoperated switch 26 may be connected in series between the power supply25 and the ground conductor 24 to disconnect the source of power whenthe circuit is not being used. The switch is a safety means for insuringthat leakage current cannot flow in the circuit. It is not necessary fornormal operation because when there is no current passing through thetarget, there is no current flowing elsewhere in the circuit.

The coupling circuit includes a controlled rectifier 27 and aunijunction transistor 28. A firing electrode 30 of the controlledrectifier 27 is coupled through a rectifier diode 31 and a capacitor 32to the junction between conductor 18 and one side of lamp 23. Thiscircuit transmits a pulse to the rectifier 27 causing it to conduct andsend current from the positive conductor 22 through rectifier 27 andresistor 33, thereby applying a positive potential over conductor 34 toresistor 35 and capacitor 36 to charge capacitor 36. Capacitor 36reaches its predetermined charging voltage after a short time intervalwhich is determined by the RC charging circuit including resistor 35 andcapacitor 36. As the voltage builds up on capacitor 36, the voltage ofthe emitter of the unijunction transistor 28 is raised until the firingvoltage is reached. At this point capacitor 36 discharges its quantityof electricity through the unijunction transistor 28 and resistor 37.

When the controlled rectifier 27 is made conductive, a positive pulse isapplied over conductors 34 and 38 to operate recorder 21. The currentthrough the controlled rectifier 27 continues to flow until theunijunction transistor is fired. The time interval between these twoevents produces a recording pulse which may be many times longer thanthe pulse received from the target 10. When the unijunction transistor28 transfers the charge from capacitor 36, the potential of conductors38 and 34 rises because of a positive pulse transmitted through diode 43and capacitor 40. This action stops conduction through rectifier 27 andthe entire circuit is normalized.

The circuit also includes a diode rectifier 41 which is put in thecircuit in order to eliminate any voltage pulses which might raiseconductors 34 and 38 above the voltage of the power supply 25. If, forany reason, an inductive kick is applied to these conductors, the excessvoltage will be transferred to the power supply whichwill absorb theadditional voltage. Another diode 42 is bridged across the recorderterminals to protect the recorder cir cuit from negative pulses whichmay be applied to conductor 38. A third diode 43 is connected betweenthe number 1 base of the unijunction transistor 28 and capacitor 40 sothat the capacitor 40 cannot discharge through the unijunctiontransistor elements and resistor 44.

Under ordinary working conditions the current pulse through lamp 23 willnot be enough to light the lamp since the pulse is too short. However,if metal screen 12 is displaced so that it makes contact with film 14and the short persists, lamp 23 will be lighted, indicating that thetarget is temporarily not in a condition to record another projectile.It has been found that a condition such as that described above willpersist for less than one second at which time the current from thestorage battery 19 will burn out the short circuit and normalize thetarget. At this time lamp 23 goes out and the circuit is ready foranoher recording operation.

As mentioned above, the target mesh electrodes are always insulated fromeach other after each penetration by battery burn out. However, theremay be rare occasions when the burn-out arc deposits impurities on thesides of the hole and creates a high resistance circuit between theelectrodes. In such a case, the recording circuit will not give a falsereading because an appreciable amount of current must be applied tocapacitor 32 and diode 31 before the controlled rectifier 27 is madeconductive.

The target described above includes three laminations of propylene foampolymer which has been cast with minute bubbles to produce the actiondesired. It is within the provisions of the invention to use othersubstances which are similar to this plastic foam and have the samemechanical and electrical characteristics. The only limitations of theinvention are therefore to be determined from the scope of the appendedclaims.

I claim:

1. A target for electrically recording the perforations caused by asurface insulated projectile comprising; a first supporting insulatorsheet composed of polypropylene foam in the form of a central flexiblepanel; electrode means secured to each side of said insulator sheet,each of said electrode means composed of a metal woven wire screen forscratching the insulation from the projectile surface and for makingelectrical contact with the projectile body as the projectile passesthrough the target; two additional flat insulator panels bonded to saidelectrodes for waterproofing the target and for increasing itsmechanical strength, said additional panels also formed of polypropylenefoam; and a recorder circuit coupled to said target electrodes forrecording each current pulse caused by a projectile making electricalcontact with both screens.

2. A target as claimed in claim 1 wherein the edges of all the plasticfoam layers are bonded together to seal the metal screen electrodes fromthe ambient space.

References Cited UNITED STATES PATENTS 3,401,939 9/1968 La Mura.2,576,960 12/ 1951 McAvoy. 2,819,084 1/1958 Brown et al. 2,819,0851/1958 Brown et al. 3,004,763 10/ 1961 Knapp. 3,172,072 3/1965 Willy161-159 X 3,215,933 11/1965 Scanlon. 3,220,902 11/1965 Edwards 161--161X ANTON O. OECHSLE, Primary Examiner.

M. R. PAGE, Assistant Examiner.

